Exhaust muffler comprising a catalytic converter

Abstract

The invention relates to an exhaust-gas muffler on an internal combustion engine in a motor chain saw. The exhaust-gas muffler includes a housing ( 1 ) which is assembled of two housing shells ( 2, 3 ). The one housing shell ( 2 ) has an exhaust-gas inlet ( 4 ) and the other housing shell ( 3 ) has an exhaust-gas outlet ( 5 ). An inner wall ( 8 ) as well as a catalytic converting element ( 7 ) are provided in the inner space ( 6 ) of the muffler housing ( 1 ). The catalytic converting element ( 7 ) is mounted between the exhaust-gas inlet ( 4 ) and the exhaust-gas outlet ( 5 ). In order to ensure an adequate catalytic converting treatment of the exhaust gas at low gas counterpressure, it is provided to divide the entering exhaust-gas flow ( 10 ) and to conduct at least one of these component flows ( 23 ) in contact with the catalytic converting element ( 7 ). The component flows ( 22, 23 ) are brought together and mixed with other before exiting from the muffler housing ( 1 ).

What is claimed is:  
     
       1. An exhaust-gas muffler on an internal combustion engine of a work apparatus including a motor-driven chain saw, the engine having an exhaust-gas channel through which the exhaust gas is discharged, the exhaust-gas muffler comprising: 
       a muffler housing including first and second housing shells;  
       said first housing shell having an exhaust-gas inlet communicating with said exhaust-gas channel for receiving the inflowing exhaust gas flow;  
       said muffler housing including an exhaust-gas outlet for conducting the exhaust gas out of said muffler housing;  
       a catalytic converting element disposed between said exhaust-gas inlet and said exhaust-gas outlet; and,  
       means for guiding a first component flow of said inflowing exhaust-gas flow in contact with said catalytic converting element and a second component flow of said inflowing exhaust gas flow essentially without contact with said catalytic converting element and for bringing said first and second component flows together and for mixing said component flows together before said component flows exit through said exhaust-gas outlet from said housing.  
     
     
       2. The exhaust-gas muffler of  claim 1 , wherein the exhaust-gas flow is subdivided immediately after entry into the muffler housing into said first component flow and said second component flow. 
     
     
       3. The exhaust-gas muffler of  claim 1 , said guiding means including at least one conducting wall connected to the exhaust-gas inlet and guiding the exhaust-gas flow. 
     
     
       4. The exhaust-gas muffler of  claim 3 , wherein the conducting wall extends through the muffler housing in the inflow direction of the exhaust gas and lies against the housing shells. 
     
     
       5. The exhaust-gas muffler of  claim 4 , wherein the conducting wall is defined by an inlet pipe having a pipe surface in which a plurality of outflow openings is introduced in the form of a showerhead. 
     
     
       6. The exhaust-gas muffler of  claim 5 , wherein the inlet pipe has an approximately oval cross section and is closed at its ends by the housing shells; and, receiving sleeves for assembly screws, the receiving sleeves pass through the inlet pipe and are arranged especially parallel to the longitudinal axis of the inlet pipe. 
     
     
       7. The exhaust-gas muffler of  claim 6 , wherein a part of the outflow openings opens into the catalytic converting element which is carried by the conducting wall configured as an inlet pipe. 
     
     
       8. The exhaust-gas muffler of  claim 1 , wherein the catalytic converting element is made of a housing pot which includes a catalytically effective material and is made of a catalytically converting coated material. 
     
     
       9. The exhaust-gas muffler of  claim 8 , wherein said muffler housing includes an intermediate wall which partitions the interior space of the muffler housing transversely to the inflow direction of the inflowing exhaust gas flow into first and second chambers separate from each other, the chambers communicating with each other via connecting openings in the intermediate wall; and, the inlet pipe projects through the intermediate wall and the outflow openings open into the first chamber and the second chamber. 
     
     
       10. The exhaust-gas muffler of  claim 9 , wherein the catalytic converting element lies in the intermediate wall and the treated exhaust gas can flow off into the first chamber and/or the second chamber. 
     
     
       11. The exhaust-gas muffler of  claim 1 , wherein said guiding means comprises: two conducting walls arranged to lie approximately parallel to each other; the conducting walls delimiting an inlet shaft into which the exhaust-gas inlet opens; and, at least one of the conducting walls carrying a coating of a catalytic converting material. 
     
     
       12. The exhaust-gas muffler of  claim 11 , wherein receiving sleeves are arranged in the inlet shaft for assembly screws; the receiving sleeves extend through the muffler housing and fill the distance (a) between the conducting walls with a pregivable play (s); and, showerhead-like outflow openings are formed in at least one of the conducting walls. 
     
     
       13. The exhaust-gas muffler of  claim 12 , wherein said guide means includes an intermediate wall which partitions the inner space of the muffler housing transversely to the inflow direction of the exhaust gas flow into inlet end and outlet end chambers, which communicate with each other via a connecting opening; and, an inlet shaft projects through the intermediate wall and the outflow openings open into the inlet end chamber. 
     
     
       14. The exhaust-gas muffler of  claim 13 , wherein the conducting walls form legs of a U-shaped bracket having a base leg which has an inflow opening lying coincident to the exhaust-gas inlet. 
     
     
       15. The exhaust-gas muffler of  claim 1 , wherein said housing comprises an intermediate wall which partitions the inner space of the muffler housing transversely to the inflow direction of the exhaust gas flow into an inlet end chamber and an outlet end chamber separate from each other; the intermediate wall has first and second connecting openings between the two chambers and, the catalytic converting element is mounted in the flow path of a connecting opening and lies in the outlet end chamber. 
     
     
       16. The exhaust-gas muffler of  claim 15 , wherein the catalytic converting element comprises a plurality of catalytic converter sheet metal pieces lying approximately parallel to each other; the catalytic converting sheet metal pieces are inserted via holding flags formed thereon in receiving slits of a holding angle and are assembled to a component unit and lie approximately perpendicularly to the intermediate wall and the holding angle is fixed at the intermediate wall. 
     
     
       17. The exhaust-gas muffler of  claim 15 , wherein the second connecting openings open between the catalytic converter sheet metal pieces and throughflow openings are formed in the catalytic converting sheet metal pieces. 
     
     
       18. The exhaust-gas muffler of  claim 15 , wherein said guide means comprises the conducting wall as an interior wall to subdivide the muffler housing in the inflow direction of the exhaust gas flow and the exhaust gas is guided transversely to the inflow direction along the conducting walls from the exhaust-gas inlet to the exhaust-gas outlet; the conducting wall is transverse to the inflow direction of the exhaust gas flow and lies at a distance (y) to the wall of said muffler housing. 
     
     
       19. The exhaust-gas muffler of  claim 18 , wherein the exhaust-gas flow is guided transversely to the inflow direction in a partially circular-shape or spiral-shape about the exhaust-gas inlet to the exhaust-gas outlet. 
     
     
       20. The exhaust-gas muffler of  claim 1 , said muffler housing including an intermediate wall which partitions the inner space of the muffler housing transversely to the inflow direction of the exhaust gas into two separate chambers; and, said guide means comprising a flow pipe held on the intermediate wall and connecting the chambers to each other; said catalytic converting element including a catalytic converting sheet metal piece, which is coated on both sides; the catalytic converting sheet metal piece extending in the longitudinal direction of the flow pipe and is held in the flow pipe in the region of its longitudinal edges. 
     
     
       21. The exhaust-gas muffler of  claim 20 , wherein the flow pipe is subdivided by the catalytic converting sheet metal piece essentially into two spatially separate flow paths which extend in the longitudinal direction of the flow pipe. 
     
     
       22. The exhaust-gas muffler of  claim 21 , wherein the catalytic converting sheet metal piece is twisted about the longitudinal center axis of the flow pipe in a screw shape and is preferably uniformly twisted. 
     
     
       23. The exhaust-gas muffler of  claim 22 , wherein the catalytic converting sheet metal piece has a total angle of rotation of approximately 540° to 900° over the length of the flow pipe. 
     
     
       24. The exhaust-gas muffler of  claim 23 , wherein the flow pipe, at one end, has an entry opening connected to the one chamber and, at the other end, has an exit opening connected to the other chamber; and, the catalytic converting sheet metal piece extends essentially from the entry opening to the exit opening. 
     
     
       25. The exhaust-gas muffler of  claim 24 , wherein the flow pipe lies approximately parallel to the intermediate wall. 
     
     
       26. The exhaust-gas muffler of  claim 25 , wherein the inter mediate wall comprises two component walls which are approximately parallel to each other and the flow pipe is held between the component walls. 
     
     
       27. The exhaust-gas muffler of  claim 26 , wherein the flow pipe is assembled from two pipe halves; the one pipe half is preferably configured as one piece in the one component wall and the other pipe half is preferably configured as one piece in the other component wall. 
     
     
       28. The exhaust-gas muffler of  claim 27 , wherein the longitudinal edges of the catalytic converting sheet metal piece are held clamped between the pipe halves in the region of the partition plane.